The project I am doing is single 211. For the 211 drive, I preferred to use VT 25 as a driver. I tried to make a regulator to
The project I am doing is single 211. For drive, I preferred to use VT 25 . I tried to make a regulator to feed the VT 25 filament.
The project I am doing is single 211. For drive, I preferred to use VT 25 . I tried to make a regulator to feed the VT 25 filament.
If soldering is as it looks, then a good place to start looking for trouble is at each solder joint.
Everything looks right. . There is no rippling in filimant voltage . In the VT25 voltage line, ez80+. 4 h filter + MOSFET to remove the rippling... but pleas look at oscope,,,,,,,50 mv of 50hz hum in a of vt25.!!!!!
Both tubes have the same 50Hz hum value., this device is under construction and the power part has not been started .
Is the 50 millivolts hum .. can heard in the speaker? I have 801.....10y.....and several types of VT25 tubes, all of which had the same response.
; Does anyone have experience with VT25...have they measured its output with a scope?
4 regulators made for dht tubes.....the current source circuit uses a MOSFET, but the capacitor multiplier is a bipolar transistor. These regulators are precisely tested. They do not have any hums in the output.
Your oscilloscope says 2.27 kHz hum.
You have quite a few runs of wires that are snaking around your build. I suspect these wires, which act as antennae, are picking up electrical signals that you have floating around your room. These signals could be emanating from electrical equipment that you have operating.
Try to identify wire pairs which form circuits (loops) and twist them tightly together. This will reduce the loop areas so they do not act as antennae (both receiving and transmitting).
You might try turning off all the electrical equipment in your room to see if it has any effect.
You have quite a few runs of wires that are snaking around your build. I suspect these wires, which act as antennae, are picking up electrical signals that you have floating around your room. These signals could be emanating from electrical equipment that you have operating.
Try to identify wire pairs which form circuits (loops) and twist them tightly together. This will reduce the loop areas so they do not act as antennae (both receiving and transmitting).
You might try turning off all the electrical equipment in your room to see if it has any effect.
Thank you very much... I did exactly the same thing. But it didn't have the least effect. I test about the wires.😍
thanks .... I did this but it didn't work at all. I will do it again with 0.47 capacitor////
The 50 Hz hum is usually from the power transformer. the distance between the power transformer and vt25 is about 35c m . the noise level of the hum is exactly the same in both tubes. I built a phono stage and the distance between the transformer and first tube was 15 cm. I will remove the transformer from the chassis soon. thanks for your replay.
.no hum in g of vt25 as input .....no hum in filimant . no hum in hv .......but 50 mv of 50hz hum on anode of vt25.
filimant of vt 25.....
anode of vt25...
filimant of vt 25.....
anode of vt25...
What anode load do you have, resistor, choke, transformer?
How are you biasing vt25? Fixed bias, self bias? If self biased, what value the cathode resistor have?
Try to increase filtering of the filament supply, a simple capacitor, if the hum does not disappear, at least will have a smaller amplitude. I know it sounds strange to cure anode hum by increasing heater filtering, but it always works.
I usually build the amplifier, and measure the hum at output, then adjust the driver's heater filtering for lowest hum.
How are you biasing vt25? Fixed bias, self bias? If self biased, what value the cathode resistor have?
Try to increase filtering of the filament supply, a simple capacitor, if the hum does not disappear, at least will have a smaller amplitude. I know it sounds strange to cure anode hum by increasing heater filtering, but it always works.
I usually build the amplifier, and measure the hum at output, then adjust the driver's heater filtering for lowest hum.
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used dht filimant regr..... please look at oscope pic .also i test filimant with battery... no diffrent .as you now full wave bridge rectifier use in dc circuit for filmant power....... so hum shuld be 100 hz not 50 hz.... lode is resistor.
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Try and leave oscilloscope probe in air, not connected to anything. Are you picking same 50Hz hum?
If yes, the answer is simple, the hum is coming from your AC grid.
If yes, the answer is simple, the hum is coming from your AC grid.
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oscope probe in air ...like antenna.........but main problem is electricity network or ac grid. I arranged a test today.....Please look.....